Four-Piece Mino.

How it goes together

Start from a Tenshukaku Mino: king 8g, silver 7h, golds 5h and 6i, bishop 8h, and the right silver out on 5g. That silver goes up to 6f and then diagonally back to 7g, beside the king. The bishop steps back to 7i first, because a silver on 7g would block its diagonal from 8h. Then the sixth-file pawn steps up to 6f and the 5h gold climbs to 6g. The 7g silver guards the 8f pawn on the king’s head and the 7f and 6f pawns; the 7h silver and the 6g gold both guard it, and the 6i gold guards the 7h silver and the bishop.

A Four-Piece Mino is a Tenshukaku Mino with five more moves: the first eleven below are that castle.

Move by move

Black only, from the start position. The first eleven moves are the Tenshukaku Mino; the last five follow the Japan Shogi Association’s column, and a shogi-gym game record plays them in the same order.

Sixteen moves. Two silvers and two golds now stand around the king, and the bishop has given up 8h to make room.

What it is good against

The head and the diagonal beside it. Shogi Wars says the 7g silver repairs what a Tenshukaku Mino lacks: the 8f pawn on the king’s head is now guarded by the silver as well as the king, and 7f by the silver, the 6g gold and the king. The JSA column says that with the 7g silver and the 6f pawn shutting out the opponent’s bishop, the castle is more solid and thicker above.

Where it breaks

Time, and the attack. It takes five more moves after a Tenshukaku Mino, and the JSA column warns that the opponent often answers the silver’s step back to 7g with a pawn to 6e, so the 6f pawn and the 6g gold may never get there. With both silvers defending, shogi-joutatsu says, the attack is thin.

When to build it

A static rook castle against a ranging rook, built from a Tenshukaku Mino when there is time. ja.wikipedia says the Left Silver Crown evolved from it, and the JSA column takes it one step further, into the Yonenaga King.